1. Field of the Invention
The present invention relates to photographic printers, and in particular, it relates to the use of a vacuum platen in advancing photographic print paper.
2. Description of the Prior Art
Many photographic printers are designed and used for short run printing. Typically, these types of photographic printers are used by professional studios which use many widths of print paper, depending on the size of the prints desired by the customer.
These printers typically include an interchangeable internal print paper supply generally stored in a light-proof cannister. To produce different sizes of prints, the appropriate cannister with the proper width of print film is placed in the printer. Each time the print paper is changed, the print paper must be threaded through drive rollers which move the print paper through an exposure station. The exposure is then made on the print paper and the print paper is indexed and another exposure is made adjacent the first. This procedure is followed until the run is done and the next cannister containing a different width of photographic print paper is placed into the printer.
Generally, each run is a short run and at the beginning of each run there is a leader section of photographic print paper between the first exposure and the leading edge of the print paper that is not exposed and is cut off as waste. Due to the short runs, this wasted print paper amounts to a significant portion of the roll.
There has been much work in paper advance systems in the photographic and related industries. Some of that work has included the use of vacuum in handling either film or print paper.
For example, the Taini U.S. Pat. No. 2,804,304 describes a device that has a number of air suction slots to handle prints. The Brueuers et al U.S. Pat. No. 2,600,469 and the Anander U.S. Pat. No. 2,753,181 disclose vacuum cylinders for handling web material. The Mason et al U.S. Pat. No. 3,536,401 and the Roberts et al U.S. Pat. No. 3,721,375 show moving vacuum belts for transporting paper. In the Wolf et al U.S. Pat. No. 3,468,606 a vacuum is used to hold together two moving webs. In the Horn U.S. Pat. No. 2,292,521, the Rabinow U.S. Pat. No. 3,220,723 and the Wossler U.S. Pat. No. 4,177,983 suction devices are used to separate and lift various sheets of material. Vacuum platens are described in the Cooper U.S. Pat. No. 2,892,379, the Flynn et al U.S. Pat. No. 3,379,436, the Nothmann et al U.S. Pat. No. 3,689,150 and the Wiessner U.S. Pat. No. 3,966,320 as devices to hold film flat in cameras. Vacuum platens are also described in the Bernstein et al U.S. Pat. No. 3,890,045 and the Gross U.S. Pat. No. 3,936,185 as backing devices for holding paper and film flat in photographic printers.